While soybeans provide a high-quality protein, and there are increasing reports of health benefits from consuming soy protein products (FDA, 1999), the demand for soybeans in human foods has not been large. In 1971, less than one percent of the U.S. soybean crop was used as a protein source for human foods (Wolf and Cowen, 1971) and in 1999, this value was about the same (Soy Source, 1999). This is largely due to the undesirable flavor and odor associated with soy products (Kinsella, 1979; McLeod and Ames, 1988; Wilson et al., 1990; Freese, 1999). Jorge et al. (1999) demonstrated that the introduction of as little as two-percent powdered soymilk into chocolate significantly lowered sensory scores, with levels above six percent being deemed unacceptable. Incorporating soy protein isolate (SPI) at a level of two percent into frankfurters significantly lowered sensory scores (He and Segranek, 1996).
Boatright and Lei (2000) employed gas chromatography/olfactometry (GCO) to identify major odorants from the headspace of aqueous solutions of soy protein isolates (SPI) using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were dimethyl trisulfide (DMTS); methanethiol; hexanal; an unidentified charred sweaty feet-like odor; 2-pentyl furan; 2,3-butadione; and an unknown burnt-like odor. The most powerful odorants by static headspace analyses were dimethyl trisulfide, hexanal, methanethiol and 2-pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs on a dry basis. This corresponds to odor values of 301 and 228, respectively in the 5% aqueous SPI slurries.
There is, therefore, a need for methods of reducing the odor associated with soy products and compositions containing soy products having reduced odor and improved flavor.